Raffaele Bombelli (1526-1573) took this concept even further by considering
the cubic , which was known to have 4 as the only positive root.
Nonetheless, Cardan's formula produced the solution
. Bombelli considered the
following identity: , which brought him to
the conclusion that . Thus imaginary
or *fictitious* numbers found some practical use.

Thu Feb 26 17:04:11 CET 1998